Unable to boot into anything but Windows 10

I had a working dual-boot (openSUSE Leap 42.2 and Windows 10) system until an hour ago. Then I tried to boot from a gparted-live DVD (gparted-live-0.30.0-1-amd64 to be precise). The system failed to boot this supposedly bootable disc but went straight into Windows. Now whenever I boot/reboot the system it just goes into Windows whether I have a bootable DVD in or not. Also whether I am holding the f9 or f10 keys down or not, i.e. I can’t seem to get into the BIOS either. This is a UEFI machine.

Please can someone tell me how to fix this and get back my boot menu and get access to the BIOS.

What about F12 (during boot). On some computers, that brings up a boot menu.